Re: [Qemu-devel] [RFC PATCH COLO v2 05/13] quorum: implement block driver interfaces for block replication

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/03/2015 10:36, Wen Congyang wrote:
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  block/quorum.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
> 
> diff --git a/block/quorum.c b/block/quorum.c
> index d087135..eee829d 100644
> --- a/block/quorum.c
> +++ b/block/quorum.c
> @@ -84,6 +84,8 @@ typedef struct BDRVQuorumState {
>                              */
>  
>      QuorumReadPattern read_pattern;
> +
> +    int colo_index; /* store which child supports block replication */
>  } BDRVQuorumState;
>  
>  typedef struct QuorumAIOCB QuorumAIOCB;
> @@ -1024,6 +1026,7 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
>      }
>  
>      g_free(opened);
> +    s->colo_index = -1;
>      goto exit;
>  
>  close_exit:
> @@ -1114,6 +1117,78 @@ static void quorum_refresh_filename(BlockDriverState *bs)
>      bs->full_open_options = opts;
>  }
>  
> +static void quorum_stop_replication(BlockDriverState *bs, Error **errp);
> +static void quorum_start_replication(BlockDriverState *bs, COLOMode mode,
> +                                     Error **errp)
> +{
> +    BDRVQuorumState *s = bs->opaque;
> +    int count = 0, i, index;
> +    Error *local_err = NULL;
> +
> +    /*
> +     * TODO: support COLO_SECONDARY_MODE if we allow secondary
> +     * QEMU becoming primary QEMU.
> +     */
> +    if (mode != COLO_MODE_PRIMARY) {
> +        error_set(errp, QERR_INVALID_PARAMETER, "mode");
> +        return;
> +    }
> +
> +    if (s->read_pattern != QUORUM_READ_PATTERN_FIFO) {
> +        error_set(errp, QERR_INVALID_PARAMETER, "read pattern");
> +        return;
> +    }
> +
> +    for (i = 0; i < s->num_children; i++) {
> +        bdrv_start_replication(s->bs[i], mode, &local_err);
> +        if (local_err) {
> +            error_free(local_err);
> +            local_err = NULL;
> +        } else {
> +            count++;
> +            index = i;
> +        }
> +    }
> +
> +    if (count == 0) {
> +        /* No child supports block replication */
> +        error_set(errp, QERR_UNSUPPORTED);
> +    } else if (count > 1) {
> +        quorum_stop_replication(bs, NULL);
> +        error_setg(errp, "too many children support block replication");
> +    } else {
> +        s->colo_index = index;
> +    }
> +}
> +
> +static void quorum_do_checkpoint(BlockDriverState *bs, Error **errp)
> +{
> +    BDRVQuorumState *s = bs->opaque;
> +
> +    if (s->colo_index < 0) {
> +        error_setg(errp, "Block replication is not started");
> +        return;
> +    }
> +
> +    bdrv_do_checkpoint(s->bs[s->colo_index], errp);
> +}
> +
> +static void quorum_stop_replication(BlockDriverState *bs, Error **errp)
> +{
> +    BDRVQuorumState *s = bs->opaque;
> +    int i;
> +
> +    if (s->colo_index >= 0) {
> +        bdrv_stop_replication(s->bs[s->colo_index], errp);
> +        s->colo_index = -1;
> +        return;
> +    }
> +
> +    for (i = 0; i < s->num_children; i++) {
> +        bdrv_stop_replication(s->bs[i], NULL);
> +    }

Why do anything at all if s->colo_index < 0?  So, with the for loop
removed (and possibly the if condition changed to "s->colo_index < 0",
similar to quorum_do_checkpoint:

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo

> +}
> +
>  static BlockDriver bdrv_quorum = {
>      .format_name                        = "quorum",
>      .protocol_name                      = "quorum",
> @@ -1137,6 +1212,10 @@ static BlockDriver bdrv_quorum = {
>  
>      .is_filter                          = true,
>      .bdrv_recurse_is_first_non_filter   = quorum_recurse_is_first_non_filter,
> +
> +    .bdrv_start_replication             = quorum_start_replication,
> +    .bdrv_do_checkpoint                 = quorum_do_checkpoint,
> +    .bdrv_stop_replication              = quorum_stop_replication,
>  };
>  
>  static void bdrv_quorum_init(void)
>